The Flash Season 2 Episode 17
After Cisco and them found that Jay is Zoom, Barry try to figure out himself how to increase his speed.
Barry thinks that he could go back to see old Harrison and asks him to teach him how to run faster. Cisco and Caitlin agree with him but Harrison-2 disagreed. He think Barry might screw the timeline.
They plan with him to keep timeline safe, he should just go talk to Harrison only. On the way Barry get distracted by some one, he shows up early in past. He takes the past Flash out and disguise as him.
Barry asks Harrison about how to improve his speed, but at the police station someone that Barry found during time travel shows up. He rush to there but he miss it.
After back to STAR lab, he thinks that Harrison starts to suspects him. He lures him to the his room and knocks him down. He knows that Barry is not from this time, he tells him that what comes after one who across the time.
He asks him about speed force, Harrison figured that his plan failed. Barry tricks him that he won and goes back home. But while Harrison is going to kill him, he bluff him that he tells real Barry the truth.
He bluffs Harrison to teach him how to get him faster, at STAR Lab time wrath shows up and chase after Cisco, Caitlin. But they manged to chase it out.
Harrison tells him that it will end him, so he needs him to figure out how to find him. After that past Barry shows up, Barry faces up with them. He tells them that Time wrath is after him, Harrison gives Barry the thumb drive and let him figure out himself.
Barry leaves and goes back to the past, he lure time wrath after him back to the future. But it comes after him, then Hartley shows up and help him chase out time wrath.